Harmonic stops have in recent years come into great favour, in the first instance through the careful and successful experiments of the eminent French builder, M. Cavaillé-Coll, of Paris. Guided by the fact that performers upon wind instruments exercise a greater pressure of wind for the production of the higher notes than the lower, the above ingenious builders applied the same principle to some of their organ registers, with the most excellent result. In this manner they produced the stops—most of which have been naturalised in England—called 'Flute Harmonique, 8 pieds,' 'Flute Octaviante, 4 pieds,' 'Trompette Harmonique, 8 pieds,' etc. At first only a few experimental pipes were made to test the soundness of the theory, for the resistance presented to the finger by the highly compressed air was so excessive as to prevent their adoption in practice; but the invention of the Pneumatic lever removed this objection, and Harmonic Stops and the Pneumatic attachment were introduced together for the first time, in Cavaillés fine organ in the abbey church of St. Denis, near Paris, finished in 1841. Very effective Harmonic Flutes, though naturally less powerful, are frequently voiced upon a wind of the ordinary strength when there is a copious supply of it.
length, but the octave to that sound. They have been known in Germany for nearly two hundred years. The 'violoncello, 8 feet pitch' on the Pedal organ at Weingarten, made in the first half of last century, is in reality 16 feet in length, of tin, and 3½ inches in diameter.
[ E. J. H. ]
[ G. ]
[ G. ]
HARMONIUM (French, also Orgue expressif). A well-known popular keyed instrument, the tones of which are produced by thin tongues of brass or steel, set in periodic motion by pressure of air, and called 'vibrators.' They are known also as 'free reeds'; reeds, because their principle is that of the shepherd's pipe; free, because they do not entirely close the openings in which they vibrate at any period of their movement, while those generally used in the organ, known as 'beating or striking reeds,' close the orifice at each pulsation. It is not however the vibration of the tongue itself that we hear as the tone: according to Helmholtz this is due to the escape of the air in puffs near its point, the rapidity of alternation of the puffs determining the pitch. The timbre of the note is conditioned in the first place by this opening, and then by the size and form of the channel above the tongue and its pallet hole, through which the air immediately passes. The Harmonium is the most modern of keyed instruments, if we include the nearly related American Organ, in which the vibrator is set in motion by reverse power, that is by drawing in the air; for if we go back to the earliest attempts to make instruments of the kind we are still within the I9th century. The usefulness and convenience of the harmonium have gone far to establish it, almost as a rival, in a commercial sense, to the pianoforte. It has been too much the practice to regard the harmonium only as a handy substitute for the organ, and this has been fostered by interested persons to the detriment of its individuality and the loss of the perception that it has reason to exist from its own merits as a musical instrument. It is true that like the organ the tones of the harmonium may be sustained at one power so long as the keys are kept down, and variety of timbre is obtained by using the stops; but when the Expression stop is used, by which the air reservoir is cut off and the pressure made to depend entirely upon the management of the bellows, the harmonium gains the power of increase and decrease of tone under the control of the player, who by the treadles can graduate the condensation of the wind almost as a violin-player manages his tone by the bow. To use this power artistically the harmonium-player must have skill; and few take to this instrument with anything like the high technical aim with which the pianoforte and violin are studied. There is however no reason that there should not be a school of composers and players competent to realise and develop the individual character of the instrument.The history of the harmonium is intimately connected with that of the different wind harmonicas which from the musical fruit and baby trumpets of Nuremberg, to accordions and concertinas, have during the past fifty years had such extensive popularity. Unlike as the whole tribe of reed organs have been to any notion of music that pertained to ancient Greece, it is not a little surprising that a large vocabulary of Greek names should have been adopted to describe them. The first name, and one still in use, that of Orgue expressif, was due to a French-